1. Field of the Invention
This invention relates to a thermal transfer printer and a print-start control method which apply print energy to a thermal head to heat the thermal head, so as to perform printing by transferring ink on a heat-melt type ink ribbon or a thermal-sublimation type ink ribbon onto a print sheet.
2. Description of Prior Art
A thermal transfer printer performs printing for one line by moving a carriage, on which a thermal head is mounted, along a platen, and after the one-line printing, feeding a print sheet for one line and performing printing for the next line. Thus, the thermal transfer printer performs a predetermined printing by repeating the above operations. This printer is widely used as an output device for a computer, a word processor and the like by virtue of high-quality printing, low noise, low cost, simple maintenance and the like.
In the thermal transfer printer, the carriage is movable along the platen, and the thermal head having a plurality of arrayed heat generating elements is mounted on the carriage, further, a ribbon cassette containing a desired color ink ribbon is removably attached to the carriage. The ink ribbon fed from the ribbon cassette and a print sheet are held between the platen and the thermal head, then the thermal head with the carriage is moved along the platen, while the ink ribbon is reeled up, on the other hand, the heat generating elements of the thermal head are selectively electrify-driven based on image information to generate heat, thus desired printing is performed by partially transferring the ink on the ink ribbon onto the print sheet.
Generally, the thermal transfer printer performs printing by using a heat-melt type ink ribbon, formed by coating a substrate of a plastic film or the like with heat-melt type ink, as the ink ribbon. Recently, a thermal transfer printer which performs printing by using a thermal-sublimation type ink ribbon, formed by coating the above substrate with thermal-sublimation type ink, has also been proposed.
The thermal transfer printer, which performs printing by using the heat-melt type ink ribbon, can perform printing on various types of paper such as a normal print sheet, a cardboard and a post card, thus can be used for various purposes. Further, the thermal transfer printer, which performs printing by using the thermal-sublimation type ink ribbon, uses a special paper having a processed surface, and controls the amount of ink sublimation to control an ink amount transferred onto the special paper, by controlling energy applied to the thermal head, for density control of printed image on the special paper, thus obtains a high-quality full color image which is a good match for a silver-chloride photograph. For this feature, in recent years, the thermal-sublimation type printer has been widely used as a high image-quality video printer or the like.
Further, in recent years, a thermal transfer printer corresponding to both heat-melt type ink ribbon and thermal-sublimation type ink ribbon has been proposed.
However, this thermal transfer printer has the following problem. For example, immediately after print start, if the temperature of the thermal head has not risen to a temperature to permit ink transfer from the ink ribbon onto a print sheet, even though the heat generating elements of the thermal head are selectively caused to generate heat, an excellent printing is not obtained.
To prevent this inconvenience, it has been considered to perform control such that before print start, the heat generating elements of the thermal head are heated in advance.
However, the conventional print temperature control simply heats the thermal head before print start, and only determines whether or not the thermal head temperature has become a print-enable temperature or higher. If the thermal head temperature is higher than the print-enable temperature, printing is started. However, in this control, even if the thermal head temperature is too high to perform printing, the above control cannot determine this situation. Further, occasionally, printing is performed when the thermal head temperature is further increasing. In any way, printing after such determination of the thermal head temperature might not obtain an excellent result.
Especially, in printing using the thermal-sublimation type ink ribbon, the sublimation amount of the thermal-sublimation type ink is controlled by heat generation of the heat generating elements of the thermal head to control the ink amount transferred onto the print sheet. To obtain an excellent print result, management of the thermal head temperature in printing is necessary.